Enhanced wear resistance of orthopaedic bearing due to the cross-linking of poly(MPC) graft chains induced by gamma-ray irradiation

Masayuki Kyomoto, Toru Moro, Fumiaki Miyaji, Tomohiro Konno, Masami Hashimoto, Hiroshi Kawaguchi, Yoshio Takatori, Kozo Nakamura, Kazuhiko Ishihara

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35 Citations (Scopus)


We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPEg-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The dynamic coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups.

Original languageEnglish
Pages (from-to)320-327
Number of pages8
JournalJournal of Biomedical Materials Research - Part B Applied Biomaterials
Issue number2
Publication statusPublished - 2008 Feb


  • Joint replacements
  • Phosphorylcholine
  • Polyethylene
  • Sterilization


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